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Transcript of Stroboscopic Effects
DESIGN AND CONSTRUCTION OF A TWIN FLUORESCENT FITTING TO REDUCE STROBOSCOPIC
EFFECT IN WORKSHOPS
SULEIMAN A. A SALIFU 01052249D
ISHMAEL QUAYSON MBIR 01052206D
SUBMITTED IN PARTIAL FULFILMENT FOR THE AWARD OF HIGHER NATIONAL DIPLOMA IN ELECTRICAL/ELECTRONICS
ENGINEERING
DEPARTMENT OF ELECRICAL/ELECTRONICS ENGINEERING ACCRA POLYTECHNIC
SEPTAMBER 2008
CERTIFICATION BY SUPERVISOR
I hereby certify that this project work was carried out under my
supervision. I therefore approve that the work is adequate in scope
and quality for the partial fulfillment of the requirement for the award
of a Higher National Diploma (HND) in Electrical/Electronics
Engineering.
SUPERVISOR:
SIGN…………………………….
DATE……………………………
I
DEDICATION
This project is dedicated to
II
DECLARATION
I ………………………………………………….. Declares that the work
was undertaken whilst in Accra Polytechnic.
I further affirm that, this work so far as I know has not been
submitted to any institution for the award of any certificate and the
source of information has been fully acknowledged
NAME………………………………………..
SIGN…………………………….
DATE……………………………
III
ACKNOWLEDGEMENT
IV
ABSTRACT
The project in question is a Twin Fluorescent Fitting to Reduce
Stroboscopic Effect in Workshops.
The report is to investigates and solve the visual illusions caused by
the stroboscopic effects of lighting on rotating and reciprocating
machinery. The lamps studied were fluorescent, mercury vapor, and
incandescent. The results from the experimentation showed
stroboscopic effects for the fluorescent and the mercury vapor
lamps. No stroboscopic effects were observed from the
incandescent lamps.
The lights are powered by the same source of a power, but are
timed to a different frequency to create variation in movement of the
rotating part of the machine.
V
TABLE OF CONTENTS
CONTENT PAGE
CHAPTER ONE
1.1 INTRODUCTION 1
1.2 BACKGROUND 2
1.3 DEFINATION 3
1.4 OBJECTIVES 4
1.5 SIGNIFICANCE OF STUDY 5
1.6 METHOLOGY 6
CHAPTER TWO
2.1 7
VI
CHAPTER THREE
3.1
CHAPTER FOUR
4.1 GENERAL MODE OF OPERATION
4.2 IMPORTANT
4.3 PRECAUTIONS
4.4 SUMMARY
4.5 RECORMENDATIONS
REFERNCE
VII
CHAPTER ONE
1.1 INTRODUCTION
In an installation where rotating machinery is present and where
discharge lamps are used, there is a risk that, the raotating parts
may appear stationary. This effect is known as stroboscopic effect.
It only occurs on discharge lamp, because their discharge is being
extinguished twice every cycle, which causes them to flicker 10ms.
This does not happen in incandescent lamps because their filament
does not cool fast enough to show any signed of cycle variation.
The simplest way to understand stroboscopic effect is to consider
the spoke of rotating wheel. At the moment in time the discharge
lamp is receiving zero voltage, a spoke is always in the position that
was occupied by another spoke whose particular time difference is
equal to one half-cycle of the supply frequency.
1
1.2 BACKGROUND
With the achievement of technological aspect, the present
inventions are relative to stroboscopic effects. These effects can be
minimized by two methods.
If a three phase supply is available this effect can be reduced by
connecting the lamps to alternate phase. As the lamp attain their
maximum and minimum values of light output in sequence, the
overall illumination is kept practically constant thereby keeping the
stroboscopic effect to minimum.
If a single-phase supply is available the head-lag circuit can be
used. In this case we are not going to deal with the single-phase.
The construction of a twin circuit these lamps A and B are supplied
by an oscillating source with frequency different from that of the
phase supplied to the machine.
2
1.3 DEFINITION
The mentioned project is a twin fluorescent light which is oscillated
to different frequency as compared to the frequency of the supply
power to the rotating machine to make a rotating part of a machine
visible.
Even though most industrial machine uses three phase supply,
there’s no guarantee that the problem could be solved by giving the
lighting system to a single phase out of the three. Lamps like
filament bulbs could had been used to solve this problem because
the coil in the bulbs does not cool down, but because of the high
power loss, heat and power consumption it also has become
impossible that type of light to be approved for our industries.
The best way so far is to construct a twin fluorescent lighting system
which is powered with power supply with different frequency from
the main supply.
3
1.4 OBJECTIVES
The main objective of this is to keep stroboscopic effect in Ghana in
to minimum such as our industries and local workshop where there
is so much revolving machines operating all the time.
The aim of this project is to minimize the dangerous situation which
could let ignorant people come in contact with these rotating parts.
4
1.5 SIGNIFICANCE OF STUDY
The main significance of this project is that:
1. the lighting system is easy to operate
2. the system is lass expensive as compared to hazards that
this project helps to avoid
3. it consumes less expensive and consumes less power.
5
1.6 METHODOLOGY
The required electronics components for this project shall be
acquired from a market at hand and the rest imported via Maplin
Electronics UK.
All important information needed for this project to takeoff was
acquired form two main source namely primary and secondary
sources.
Primary source were sources were the personal interactions with my
supervisor and workers of a well equipped and well knowledgeable
on this project.
Secondary sources were the research at the library and the internet.
6
CHAPTER TWO
2.1 TEMPORAL ALIASING
Temporal aliasing is the term applied to a visual phenomenon also
known as the stroboscopic effect. It also accounts for the "wagon-
wheel effect", so called because in video or motion pictures, spoke
wheels on horse-drawn wagons sometimes appear to be turning
backwards.
Temporal aliasing is one example of a range of phenomena called
aliasing that occur when continuous motion is represented by a
series of short or instantaneous samples. It occurs when (a) the
view of a moving object is represented by a series of short samples
as distinct from a continuous view, and (b) the moving object is in
rotational or other cyclic motion at a rate close to the sampling rate.
7
2.2 EXPLANATION
Consider the stroboscope as used in mechanical analysis. This may
be a "strobe light" that is fired at an adjustable rate. Suppose you
are looking at something rotating at 60 revolutions per second: if you
view it with a series of short flashes at 60 times per second, each
flash illuminates the object at the same position in its rotational
cycle, so it appears that the object is stationary. Furthermore, at a
frequency of 60 flashes per second, persistence of vision smoothes
out the sequence of flashes so that the perceived image is
continuous.
If you view the same rotating object at 61 flashes per second, each
flash will illuminate it at a slightly earlier part of its rotational cycle.
Sixty-one flashes will occur before you see the object in the same
position again, and you will perceive the series of images as if it is
rotating backwards once per second.
The same effect occurs if you view the object at 59 flashes per
second, except that each flash illuminates it a little later in its
rotational cycle and so, it seems to be slowly rotating forwards.
In the case of motion pictures, action is captured as a rapid series of
still images and the same stroboscopic effect can occur.
8
2.3 WAGON-WHEEL EFFECT
The wagon-wheel effect, (alternatively, or stagecoach-wheel effect,
stroboscopic effect) is an optical illusion in which a spoked wheel
appears to rotate differently from its true rotation. The wheel can
appear to rotate more slowly than the true rotation, it can appear
stationary, or it can appear to rotate in the opposite direction from
the true rotation. This last form of the effect is sometimes called the
reverse rotation effect.
The wagon-wheel effect is most often seen in film or television
depictions of stagecoaches or wagons in Western movies, although
recordings of any regularly spoked wheel will show it, such as
helicopter rotors and aircraft propellers. It can also commonly be
seen when a rotating wheel is illuminated by flickering light. These
forms of the effect are known as stroboscopic effects and they arise
from temporal aliasing: the original smooth rotation of the wheel is
visible only intermittently.
9
A version of the wagon-wheel effect can also be seen under
continuous illumination.
Wagon-wheel Effect under stroboscopic conditions
Stroboscopic conditions ensure that the visibility of a rotating wheel
is broken into a series of brief episodes in which its motion is either
absent (in the case of movie cameras) or minimal (in the case of
stroboscopes), interrupted by longer episodes of invisibility. It is
customary to call the former episodes frames. A movie camera
typically operates at 24 frames per second, and standard television
operates at 59.94 or 50 images per second (a video frame is two
separate images; see interlace.) A stroboscope can typically have
its frequency set to any value. Artificial lighting that is temporally
modulated when powered by alternating current, such as gas
discharge lamps (including neon, mercury vapor, sodium vapor and
fluorescent tubes), flicker at twice the frequency of the power line
(for example 120 times per second on a 60 cycle line). In each cycle
of current the power peaks twice (once with positive voltage and
once with negative voltage) and twice goes to zero, and the light
output varies accordingly. In all of these cases, a person sees a
rotating wheel under stroboscopic conditions. Imagine that the true
rotation of a four-spoke wheel is clockwise.
10
The first instance of visibility of the wheel may occur when one
spoke is at 12 o'clock. If by the time the next instance of visibility
occurs, the spoke previously at 9-o'clock has moved into the 12-
o'clock position, then a viewer will perceive the wheel to be
stationary. If at the second instance of visibility, the next spoke has
moved to the 11:30 position, then a viewer will perceive the wheel to
be rotating backwards. If at the second instance of visibility, the next
spoke has moved to the 12:30 position, then a viewer will perceive
the wheel to be rotating forwards, however more slowly than the
wheel is actually rotating.
The effect relies on a motion perception property called beta
movement: motion is seen between two objects in different positions
in the visual field at different times providing the objects are similar
(which is true of spoked wheels - each spoke is essentially identical
to the others) and providing the objects are close (which is true of
the originally 9-o'clock spoke in the second instant - it is closer to 12
o'clock than the originally 12-o'clock spoke). The wagon-wheel effect
is exploited in some engineering tasks, such as adjusting the timing
of an engine. This same effect can make some rotating machines,
such as lathes, dangerous to operate under artificial lighting
because at certain speeds the machines will falsely appear to be
stopped or to be moving slowly.
11
Finlay, Dodwell, and Caelli (1984) and Finlay and Dodwell (1987)
studied perception of rotating wheels under stroboscopic illumination
when the duration of each frame was long enough for observers to
see the real rotation. Despite this, the rotation direction was
dominated by the wagon-wheel effect. Finlay and Dodwell (1987)
argued that there are some critical differences between the wagon-
wheel effect and Beta motion, but their argument has not troubled
the consensus.
2.4 ETYMOLOGY
In electrical engineering, when a continuous signal is replaced by a
series of samples — say, a 24.1 Hz signal is sampled 24 times per
second — the result seems the same as if a 0.1 Hz signal were
sampled 24 times per second, so 0.1 Hz is said to be an "alias" of
24.1 Hz.
12
2.5 STROBOSCOPE
A stroboscope, also known as a strobe, is an instrument used to
make a cyclically moving object appear to be slow-moving, or
stationary. The principle is used for the study of rotating,
reciprocating, oscillating or vibrating objects. Machine parts and
vibrating strings are common examples.
In its simplest form, a rotating disc with evenly-spaced holes is
placed in the line of sight between the observer and the moving
object. The rotational speed of the disc is adjusted so that it
becomes synchronized with the movement of the observed system,
which seems to slow and stop. The illusion is caused by temporal
aliasing, commonly known as the "stroboscopic effect".
In electronic versions, the perforated disc is replaced by a lamp
capable of emitting brief and rapid flashes of light. The frequency of
the flash is adjusted so that it is equal to, or a unit fraction below or
above the object's cyclic speed, at which point the object is seen to
be either stationary or moving backward or forward, depending on
the flash frequency.
13
APPLICATIONS
Stroboscopes play an important role in the study of stresses on
machinery in motion, and in many other forms of research. They are
also used as measuring instruments for determining cyclic speed.
As a timing light they are used to set the ignition timing of internal
combustion engines.
In medicine, stroboscopes are used to view the vocal cords for
diagnosis. The patient hums or speaks into a microphone which in
turn activates the stroboscope at either the same or a slightly
different frequency. The light source and a camera are positioned by
endoscope.
Another application of the stroboscope can be seen on many
gramophone turntables. The edge of the platter has marks at
specific intervals so that when viewed by incandescent lighting
powered at mains frequency, and provided the platter is rotating at
the correct speed, the marks appear to be stationary.
Flashing lamp strobes are also adapted for pop use, as a lighting
effect for discotheques and night clubs where they give the
impression of dancing in slow motion.
14
OTHER EFFECTS
Rapid flashing can give the illusion that white light is tinged with
colour, known as Fechner colour. Within certain ranges, the
apparent colour can be controlled by the frequency of the flash, but
it is an illusion generated in the mind of the observer and not a real
colour. The Benham's top demonstrates the effect.
At certain frequencies, flashing light can trigger epileptic seizures in
some people.
STROBE LIGHT
Strobe light or stroboscopic lamp, commonly called a strobe, is a
device used to produce regular flashes of light. It is one of a number
of devices that can be used as a stroboscope. The word originated
from the Greek strobes, meaning "act of whirling."
Strobe lights have many uses, including scientific and industrial
applications, but are particularly popular in clubs where they are
used to give an illusion of slow motion (cf. temporal aliasing). Other
well-known applications are in alarm systems, theatrical lighting
(most notably to simulate lightning), and as high-visibility running
lights. They are still widely used in law enforcement and other
emergency vehicles, though they are slowly being replaced by LED
15
technology in this application, as they themselves largely replaced
halogen lighting. Strobe lighting has also been used to see the
movements of the vocal cords in slow motion during speech, a
procedure known as video-stroboscopy. Special calibrated strobe
lights, capable of flashing up to hundreds of times per second, are
used in industry to stop the motion of rotating and other repetitively-
operating machinery and to measure the rotation speeds or cycle
times. Strobelights are often used in nightclubs and raves, and are
available for home use for special effects or entertainment. A typical
commercial strobe light has a flash energy in the region of 10 to 150
joules, and discharge times as short as a few milliseconds, often
resulting in a flash power of several kilowatts. Larger strobe lights
can be used in “continuous” mode, producing extremely intense
illumination.
The light source is commonly a xenon flash lamp, which has a
complex spectrum and a color temperature of approximately 5,600
Kelvin’s. In order to obtain colored light, colored gels must be used.
16
CHAPTER THREE
3.1 Stages of Operation
There are two main stages involved in the operation of this system.
These are
1. Converting 50Hz To 0Hz (AC to DC)
2. Converting 0Hz to 50Hz (DC to AC)
3.2 Converting 50Hz to 0Hz (AC to DC)
In the conversion of the mains from 50Hz to 0Hz there three stages
involves namely
a. Stepping Down
b. Rectification
c. Smoothing
a. Stepping Down
In stepping down a transformer is used to step the voltage of the
mains from 220V/50Hz to 12Volts.
A transformer is a device that transfers electrical energy from one
circuit to another through inductively coupled electrical conductors.
A changing current in the first circuit (the primary) creates a
changing magnetic field; in turn, this magnetic field induces a
changing voltage in the second circuit (the secondary).
17
By adding a load to the secondary circuit, one can make current flow
in the transformer, thus transferring energy from one circuit to the
other.
The secondary induced voltage VS, of an ideal transformer, is scaled
from the primary VP by a factor equal to the ratio of the number of
turns of wire in their respective windings: Vs/Vp = Ns/Np
By appropriate selection of the numbers of turns, a transformer thus
allows an alternating voltage to be stepped up — by making NS
more than NP — or stepped down, by making it less.
Transformers are some of the most efficient electrical 'machines',
with some large units able to transfer 99.75% of their input power to
their output. Transformers come in a range of sizes from a
thumbnail-sized coupling transformer hidden inside a stage
microphone to huge units weighing hundreds of tons used to
interconnect portions of national power grids. All operate with the
same basic principles, though a variety of designs exist to perform
specialized roles throughout home and industry.
18
b. Rectification
Rectifier diodes are used in power supplies to convert alternating
current (AC) to direct current (DC), a process called rectification.
Bridge rectifiers
There are several ways of connecting diodes to make a rectifier to
convert AC to DC. The bridge rectifier is one of them and it is
available in special packages containing the four diodes required.
Bridge rectifiers are rated by their maximum current and maximum
reverse voltage. They have four leads or terminals: the two DC
outputs are labelled + and -, the two AC inputs are labelled .
The diagram below shows the operation of a bridge rectifier as it
converts AC to DC. Notice how alternate pairs of diodes conduct.
19
c. The Smoothing Capacitor
The full-wave bridge rectifier however, gives us a greater mean d.c. value (0.637Vmax)
with less superimposed ripple while the output wveform is twice that of the frequency
of the input supply frequency. We can therefore increase its average d.c. output level
even higher by connecting a suitable smoothing capacitor across the output of the
bridge circuit as shown below.
The smoothing capacitor converts the full-wave rippled output of the
rectifier into a smooth d.c. output voltage.
20
Two important parameters to consider when choosing a suitable a
capacitor are its Working Voltage, which must be higher than the no-
load output value of the rectifier and its Capacitance Value, which
determines the amount of ripple that will appear superimposed
ontop of the d.c. voltage. Too low a value and the capacitor has little
effect. As a general rule of thumb, we are looking to have a ripple
voltage of less than 100mV peak to peak.The main advantages of a
full-wave bridge rectifier is that it has a smaller a.c. ripple value for a
given load and a smaller reservoir or smoothing capacitor than an
equivalent half-wave rectifier. The fundamental frequency of the
ripple voltage is twice that of the a.c. supply frequency (100Hz)
where for the half-wave rectifier it is exactly equal to the supply
frequency (50Hz). The amount of ripple voltage that is
superimposed on top of the d.c. supply voltage can be virtually
eliminated by adding an an improved π-filter (pi-filter) to the ouput
terminals of the bridge rectifier. This type of low-pass filter consists
of two smoothing capacitors, usually of the same value and a choke
or inductance across them to introduce a high impeadance path to
the alternating ripple component.
21
3.2 Converting 0Hz to 50Hz (DC to AC).
The DC to AC converter also known as power inverter operates in
four stages namely (a) Regulating (b) Pulse generation (oscillating),
(c) Amplification and (d)Stepping Up.
(a)Regulating
Since the amplitude of the oscillator is determined by the Vcc. or the
power supplied to it, is very important to regulate it to match the
Gate to Source voltage of the Mosfets which would be used to
amplify the signals from the Oscillator.
The simplest voltage regulator uses just a resistor and a zener
diode. In the circuit diagram you can see a resistor (R1) and a zener
diode (ZD1) connected across a power supply. The resistor is
connected to the positive (+ve) supply wire and the zener diode
anode is connected to the zero volt (ground) wire. At the junction of
these two components the voltage is clamped by the zener diode to
its specified voltage - in this case 5.6 volts but can be changed to
9.1 or any voltage to suit the Vbe of the transistor(Mosfets) in the
amplifier.
This method is OK for low currents but the resistor becomes too hot
if larger currents are needed. To cope with this problem we can add
the NPN transistor (Q1) .
22
Now the transistor passes the current required at the output.
What is the output voltage?
It is easy to calculate. The voltage at Q1 base connection is 5.6
volts.
The voltage between base and emitter of a silicon transistor is
always 0.6 volts if the transistor is "on".
So the voltage at the Q1 emitter (Vout) must be 5.6 - 0.6 = 5.0 volts.
The output voltage will remain at a constant voltage of 5.0 volts
provided that the input voltage from the supply is more than 6 volts
(the zener voltage plus a little to compensate for that "lost" across
the resistor).
23
In fact the input voltage can be swinging up and down between, say,
6 volts and 12 volts and the output voltage at Q1 emitter will still be
a steady 5.0 volts.
The limiting factors are the amount of heat generated by R1, ZD1
and Q1 since all excess voltage must be shed as heat. The
"wattage" ratings of the individual components must be calculated to
suit:
1. The average input current (through R1 and ZD1) and the output
current (through Q1). can be calculated from Ohms Law and is
decided by whatever the regulator is to supply voltage to.
Ohms Law I = V/R
V = Volts
I = Amps if R = Ohms or
I = mA if R = k½
Let's assume the following:
The circuit which this regulator is driving needs 9.0v at a current of 200A.
A TIP41 transistor is suitable since it can handle current up to 15 A.Its gain at 40 is listed as 40 (typ) so it's easy to see that it will need at least 1mA into its base to allow 15A to flow from collector to emitter.
24
Watts = Volts x Amps milliWatts = Volts x milliAmps
Volts x Amps = Watts
Since the regulating voltage is 9volts and the maximum current from
the transistor is 15A
9volts x 15A = 135watts.
25
0V
+Ve
C2C1
Q2Q1
R4R3R2R1
(b) Pulse Generation (oscillating)
Since the DC power haves no frequency, there’s a need for an
introduction of an oscillator such as an astable multivibrator to
change the frequency from zero to 50Hz.
A multivibrator is an electronic circuit used to implement a variety
of simple two-state systems such as oscillators, timers and flip-flops.
It is characterized by two amplifying devices (transistors, electron
tubes or other devices) cross-coupled by resistors and capacitors.
The most common form is the astable or oscillating type, which
generates a square wave - the high level of harmonics in its output
is what gives the multivibrator its common name.
Astable Multivibrator circuit
26
This circuit shows a typical simple astable circuit, with an output
from the collector of Q1, and an inverted output from the collector of
Q2. Suggested values which will yield a frequency of about 48 to
50Hz:
R1, R4 = 220Ω
R2, R3 = 10K Ω
C1, C2 = 1μF
Q1, Q2 = BC547 or C945 NPN switching transistor
Basic mode of opera tion
The circuit keeps one transistor switched on and the other switched
off. Suppose that initially, Q1 is switched on and Q2 is switched off.
State 1:
Q1 holds the bottom of R1 (and the left side of C1) near
ground (0V).
The right side of C1 (and the base of Q2) is being charged by
R2 from below ground to 0.6V.
R3 is pulling the base of Q1 up, but its base-emitter diode
prevents the voltage from rising above 0.6V.
27
R4 is charging the right side of C2 up to the power supply
voltage (+V). Because R4 is less than R2, C2 charges faster
than C1.
When the base of Q2 reaches 0.6V, Q2 turns on, and the following
positive feedback loop occurs:
Q2 abruptly pulls the right side of C2 down to near 0V.
Because the voltage across a capacitor cannot suddenly
change, this causes the left side of C2 to suddenly fall to
almost -V, well below 0V.
Q1 switches off due to the sudden disappearance of its base
voltage.
R1 and R2 work to pull both ends of C1 toward +V, completing
Q2's turn on. The process is stopped by the B-E diode of Q2,
which will not let the right side of C1 rise very far.
This now takes us to State 2, the mirror image of the initial state,
where Q1 is switched off and Q2 is switched on. Then R1 rapidly
pulls C1's left side toward +V, while R3 more slowly pulls C2's left
side toward +0.6V. When C2's left side reaches 0.6V, the cycle
repeats
28
Multivibrator Frequency
Where...
f is frequency in Hertz.
R2 and R3 are resistor values in ohms.
C1 and C2 are capacitor values in farads.
T is period time (In this case, the sum of two period durations).
f is frequency in Hertz.
R2 and R3 are resistor values in ohms.
C1 and C2 are capacitor values in farads.
T is period time (In this case, the sum of two period durations).
(c) Amplification
Angle of flow or conduction angle
50% of the input signal is used (Θ = 180° or π, i.e. the active
element works in its linear range half of the time and is more or less
turned off for the other half). In most Class B, there are two output
devices (or sets of output devices), each of which conducts
alternately (push–pull) for exactly 180 deg (or half cycle) of the input
signal; selective RF amplifiers can also be implemented using a
single active element.
29
These amplifiers are subject to crossover distortion if the handoff
from one active element to the other is not perfect, as when two
complimentary transistors (i.e. one PNP, one NPN) are connected
as two emitter followers with their base and emitter terminals in
common, requiring the base voltage to slew across the region where
both devices are turned off.
The amplifier is built from a class B push to push amplifier with
independent inputs unlike the normal audio amplifier because in the
normal system, the inputs are bridged together to one input and the
output also bridged. But to obtain a angle of 3600 of input used the
two inputs has to be separated to for the inputs to swing at 90-90-
90-90 making the out put still maintained as a sinodial signal.
30
(d) Stepping Up.
For stepping up the signal amplified it is important to use a
transformer which has low power loss. One ideal type of transformer
is a sandwich double wounded transformer with laminated core.
The transformer is made 12-0-12 or 9-0-9 at the primary and 220-
240 at the secondary.
Laminated core
This is the most common type of transformer, widely used in
appliances to convert mains voltage to low voltage to power
electronics
Widely available in power ratings from 1.2w to several
kilowatts
Insulated laminations minimize eddy current losses
Most use a split bobbin, giving a high level of insulation
between the windings
Rectangular core
31
220/240V
0V
0V
9V
9V T1
Core laminate stampings are usually in EI shape pairs. Other
shape pairs are sometimes used.
Mumetal shields can be fitted to reduce EMI (electromagnetic
interference)
A screen winding is occasionally used between the 2 power
windings
Many such transformers have a thermal cut out built in, many
don't
4 turns per volt is typical for continuous use
Occasionally seen in low profile format for use in restricted
spaces
laminated core made with silicon steel with high permeability
32
3.3 Schematic Diagram
33
3.4 COMPONENT LIST
COMPONENT DESCRIPTION QUANTITY
T1 9-0-9/220V STEP-UP
TRANSFORMER
1
T2 220V /12vSTEP-DOWN
TRANSFORMER
1
ZD1 9v ZENER DIODE 1
D1 BRIDGE DIODE[GBU8M] 1
LED 1-3 LED(LIGHT EMITTING DIODE) 3
Q2-Q6 RFP40N10 4
C1,C2 15000uf 2
Q1 C2580 1
R1 1kΩ 1
SCK1 Dual 13amps 3pin 1
F1 20A Circuit Breaker 1
34
Component List for Oscillator
Q1,Q2 C945 2
C1,C2 1uf 2
R1,R4 220Ω 2
R2,R3 10KΩ 2
PCB Vero Board 1
Auxiliaries
Cable 6mm Auto flex 2
R4,R5,R7,R8 470Ω resistor
Heat sink Aluminum heat sink with fins 1
NOTE:
R - RESISTOR C - CAPACITOR
T - TRANSFORMER D - DIODE
Q - TRANSISTOR ZD- ZINER DIODE
35
3.5 CABLE SELECTION
Cables are the main material that connects on component to the
other so it is very important that the right cable is used to deliver the
right amount of power needed at a particular place.
Cables for dc applications should not be less than 6mm in diameter
and colors are also very important because to clearly explain to
someone the type of signal passing through the cable whether it is
positive or negative. For example a Red cable clearly explains that
the power passing through the cable is positive.
36
3.6 LIMITATIONS
The difficulties involved in getting the major component from an
original source was very difficult because all the companies
who manufactures these components do not sell components in
small quantities and it was very hectic getting all these
components.
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4.5 CIRCUIT CONSTRUCTION
This circuit was first divided into four stages and each stage was
carefully tested with electronics stimulator software and then
assembled.
The oscillator circuit was assembled on a Vero board (PCB) and
then tested with a signal generator and an oscilloscope to check the
frequency response. This circuit was finally tested after all he four
parts were puts together to check and correct its short falls.
Much consideration was given to meter readings or voltages and
current.
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4.6 GENERAL MODE OF OPERATION
220 volts AC (alternating current) /50Hz is connected to a
transformer to step it down to 15 volts AC. The supply is then
rectified and smoothened.
The smoothened power is then connected to an oscillator to change
its frequency back to 50Hz. The output of the oscillator is then
amplified by a push pull amplifier which has a step-up transformer to
raise the signal from 12volts AC to 220volts AC.
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4.7 PRECAUTIONS
In other to arrive at a good and a successful project, the following
precautions were taken into consideration:
1. The circuit was built under supervision to ensure accuracy.
2. The circuit diagram was first tested with schematic circuit
stimulator software and then mounted on a Vero board and
then rechecked for accuracy to prevent damage of any
component.
3. The right size of cables was used at high current lines like the
main positive input which is connected from and to the battery.
4. The entire component were thoroughly checked and tested for
consistency and efficiency.
5. Correct soldering techniques were ensured as well as the
usage of a correct solder.
6. The right tools and equipment were used for this project.
7. Suitable equivalent replacement of components was ensured
at places where the original components were not available.
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4.8 CONCLUSION
The entire project was finally concluded that; this lighting system
could enhance the sight of worker who use4s rotating machine to
caution them that there’s a rotating machine.
This project could go a long way to help reduce accident caused by
this problem in the workshop and also help in creating employment
for the youth if encouraged in the country.
41SUMMARY
From the above project it was realized that, when the supply given
to lights have different phase angle to the supply of the rotating
machine the rotating parts would be more visible to avoid accidents
in the workshop.
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RECOMMENDATIONS
My recommendations for workshops, machine shops and industries
who uses rotating machine or machines with rotating parts and also
for industries who work in the night with machines which uses three
phases.
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REFERENCES
1. Carols Advance Electronics and Training Centre.
2. www.wikipedia.com/english